1. Field of the Invention
The present invention relates to a pixel structure, a thin film transistor array, and a repairing method therefor, and more particularly to a pixel structure with a storage capacitor Cst which is adapted to be repaired, a thin film array transistor, and a repairing method therefor.
2. Description of the Related Art
Due to the advance of the semiconductor devices and display apparatuses, multimedia technology has dramatically improved. For display devices, having outstanding quality and economic advantages, Cathode Ray Tube (CRT) has dominated the display market. In the concerns of limited space required by desktop terminal/display apparatus and the environmental protection for power saving, CRT still has some issues regarding space and power consumption that should be resolved. Thus, CRT cannot meet the requirements of being slim, light and small, and power saving. Accordingly, high-resolution, effective space utilization, low-power consumption, and non-radiation Thin Film Transistor Liquid Crystal Display (TFT-LCD) has gradually become the main trend in the market.
Thin Film Transistor Liquid Crystal Display (TFT-LCD) is mainly composed of a thin film transistor array substrate, a color filter array substrate and a liquid crystal layer. Wherein, the thin film array transistor substrate is composed of transistors arranged in array and pixel electrodes corresponding thereto. The thin film transistors serve as switch devices for the liquid crystal display units. In addition, scan lines and data lines control pixels to identify the selected pixel. By applying suitable operation voltage, the data corresponding to the pixel can be displayed. In addition, generally a portion of the pixel electrode covers over the scan lines or common lines to form storage capacitors. In the prior art technology, the general storage capacitor structure has two different types: a first metal layer/insulator/a second metal (MIM) structure and a first metal layer/insulator/Metal-Insulator-ITO (MII) structure. Following are descriptions for these storage capacitors.
FIG. 1 is a cross sectional view showing a prior art MIM storage capacitor. Referring to FIG. 1, the MIM storage capacitor is composed of a scan line or a common line 100, a top electrode 120 thereon. Note that in the MIM storage capacitor, the scan line or the common line 100 is isolated from the top electrode 120 by a gate insulation layer 110. The capacitance Cst of the storage capacitor is related to the thickness of the gate insulation layer 110. In other words, the thinner the gate insulation layer 110, the larger the capacitance Cst of the storage capacitor. In addition, a pixel electrode 140 is electrically connected to the top electrode 120 through a contact window 132 within a protection layer 130.
FIG. 2 is a cross sectional view showing a prior art MII storage capacitor. Referring to FIG. 2, the MII storage capacitor is composed of a scan line or a common line 200 and a pixel electrode 230 thereon. Different from the structure of an MIM storage capacitor, in the MII storage capacitor, the scan line or the common line 200 is isolated from the pixel electrode 230 by a gate insulation layer 210 and a protection layer 220. The capacitance Cst of the storage capacitor is related to the total thickness of the gate insulation layer 210 and the protection layer 220. In other words, the thinner the total thickness of the gate insulation layer 210 and the protection layer 220, the larger the capacitance Cst of the storage capacitor.
As described, generally the capacitance Cst of an MIM storage capacitor is larger than the capacitance Cst of an MII storage capacitor. The reason is that only a gate insulation layer 110 is used in the MIM storage capacitor while a gate insulation layer 210 and a protection layer 220 are used in the MII storage capacitor.
With the storage capacitor in the pixel structure, the pixel unit of the TFT-LCD can maintain and store data. It means that the larger the capacitance Cst of the storage capacitor, the better function of storing and maintaining data by the pixel unit. Accordingly, in the prior art, the MIM storage capacitor was generally used as storage capacitor in TFT-LCD.
Though the MIM storage capacitor has larger capacitance, defects, such as particles or holes, are easily generated during the process of manufacturing the MIM storage capacitor. Accordingly, bright/dark spots will be generated and resulted in failure of the storage capacitor.